Young rhesus monkeys are currently being introduced to a novel environment at the Poolesville Animal Facility. Dr. Suomi has designed a strategy to create optimal troop size with a minimum of social conflicts. This requires discrete pairings of animals into larger and larger groups. We are collecting plasma and peripheral blood lymphocytes during specific intervals. We have observed that one animal, the behaviorally dominant individual, has higher lymphocyte activity than the other 3 in the group. This has held for two groups of 4 animals. During the course of behavioral stress challenges we have also observed that "group" lymphocyte activity is initially suppressed, rebounds and returns to baseline.